Encased coil spring units for mattresses and other reflexive support applications have long been manufactured by the use of long strips of sheet or fabric material which is folded or cut in halves and secured about a line of coil spring to form a spring unit. Various methods of attachment of the sheet material between each coil spring to and between adjacent rows or columns of encased coil springs have been used, such as stitches through the sheet material, ultrasonic welding or gluing. Because each coil spring is uniformly encapsulated in the material and also attached to the material surrounding adjacent coils, the encased coil spring unit is stabilized by the encapsulating material and provides a support structure and surface which distributes a load over a broad area relative to the primary force vector as a result of the common interconnection of the coil springs.